1. Field of the Invention
This invention pertains generally to thermal generators, and particularly, thermal generators employing thermocouples vapor-deposited on an electrically insulating carrier material.
2. Description of the Prior Art
Small, long-lasting power sources find ready application as electrical suppliers for heart pacers which are implanted in the human body. Electrochemical batteries previously used have a limited life of, at best, two years. After this time, the heart pacers must be replaced by a surgical operation.
Alternately, electrical power has been supplied through the use of thermal generators which use as their source of heat a radioactive radiator. These thermal microwatt generators should operate for many years with high efficiency and minimum space requirements.
German Auslegeschrift No. 2,002,197 describes the use of film thermocouples vapor-deposited on a ribbon-shaped electrical and thermal insulating material which combines with a radioactive radiator to make up a suitable thermal generator. The carrier is designed as a spiral winding whose one end face is connected with the heat source and whose other end face is connected directly or indirectly with the generator housing -- the latter serving as a cold heat exchanger for the generator.
The German Offenlegungsschrift No. 2,124,465 discloses a thermal generator which employs film thermocouples which are arranged on a suitable carrier adapted to be rolled-up to form a winding. Two such windings are used to form a hollow cylinder which are then positioned about the radioactive heat source. The winding is in film tape form and is only a few .mu.m thick. The thickness of the thermocouple legs, which are vapor-deposited on the carrier, is of the same order of magnitude. Because of the thinness of the tape, care must be taken that the thermocouple legs are not damaged when the winding is formed. If a break occurs in any one of the numerous thermocouple legs, the entire series circuit of the thermocouples becomes inoperative. This is a continuing problem even after the winding is completed since the mechanical strength is relatively low. Damage to a given leg can also occur during the operation of the thermal generator due either to excessive mechanical stresses, and more likely, due to excessive thermal stresses.
It is therefore a primary object of this invention to increase the handling and operational reliability of known thermal generators employing film thermocouples.